250 W

Output

Frequency	500 kHz - 80 MHz (usable down to 100 kHz)
Bands	MF through 6m (500 kHz - 80 MHz)
TX power	250 W (250W PEP or average transmit pass-through (auto-sensing TX bypass). NOT receive-only.)
Modes	all

Connectors

rf in	SO-239 (main antenna input)
rf out	SO-239 (to radio receiver/transceiver)
noise antenna	RCA phono jack (noise/sense antenna, NOT SO-239)
dc in	coaxial DC jack, 2.1mm ID, 5.0-5.5mm OD, center positive
power req	11-16 VDC, approximately 300 mA. AC-to-12VDC adapter available separately (Timewave AC-1 or similar, 300+ mA). Coaxial DC connector 2.1mm ID center positive. Reverse polarity protected.

Estimated (unverified): The ANC-4 began as a JPS Communications product (on the market by 1995); Timewave's production began in the early 2000s, but an exact introduction year is not documented. The current production version is the ANC-4+. The maker lists ~150 mA draw while the manual says ~300 mA - use a 500 mA-plus 12 V supply.

RF noise canceller: eliminates power line noise, computer noise, TV interference, motor noise 500 kHz to 80 MHz (usable to 100 kHz); covers HF through 6m 250W PEP transmit pass-through with auto-sensing TX bypass dual-antenna phase cancellation: main antenna + noise sense antenna front panel controls: Noise Phase and Noise Gain for deep null adjustment noise sense antenna via RCA phono jack (short wire included; external dipole recommended for outdoor noise) broadcast band notch filter (jumper JP3): 50+ dB attenuation of MW broadcast band also functions as active antenna (amplifies noise antenna output) also functions as diversity combiner (null interfering stations or peak weak signals) signal loss main antenna to radio: 6 dB auto TX bypass: ~7 ms on transmit detection, ~500 msec or ~7 msec return to RX 11-16 VDC, ~300 mA, reverse polarity protected originally developed by JPS Communications, now Timewave

Strengths

Cancels locally generated noise before it reaches the receiver AGC, which is more effective than DSP audio filtering that works after AGC compression. Power-line noise, plasma-TV noise, computer interference, and motor noise can be nulled substantially (the manual cites up to 50 dB). The 250 W transmit pass-through with auto-sensing bypass lets it stay inline with a transceiver. It covers 500 kHz to 80 MHz including 6 m. A broadcast-band notch filter prevents MW broadcast overload. It also works as an active antenna and a diversity combiner. The design originated at JPS Communications.

Weaknesses

The 6 dB signal loss through the unit is significant on weak signals. It requires a second sense antenna, which adds complexity. The manual phase/gain adjustment must be redone when changing bands. Nulling is frequency-specific: effective on one noise source at one frequency, not broadband. ~$270 new. Noise-antenna placement is critical; the included wire works for indoor noise, but outdoor sources need an external dipole. The ANC-5 successor adds external RX/TX control and adjustable TX hang time.

Verdict

An RF noise canceller that works ahead of the receiver. Unlike DSP filters that clean up audio after the receiver AGC has already compressed everything, the ANC-4 cancels noise at RF before it enters the receiver, which is more effective for locally generated noise. The 6 dB signal loss is the tradeoff. For operators with persistent power-line noise, computer hash, or TV interference, it can make a band usable again.

The Timewave ANC-4 is an antenna noise canceller - a box that sits between your antenna and your receiver and electronically erases a local noise source before it ever reaches the radio. It works by phasing: you connect a second, small "noise" antenna positioned to hear the offending noise - a power-line arc, a plasma TV, a switching supply - and the unit shifts that sample in phase and level until it cancels the same noise arriving on your main antenna. Done well, a strong local noise can drop by tens of decibels.

The key thing to understand is what it can and cannot do. It nulls one local, single-path noise source at a time; it does nothing for atmospheric static or for interference arriving by skywave, and you re-tune the phase and gain controls when you change bands. Because it works at radio frequency ahead of the receiver, it stops the noise from capturing the receiver's AGC - something audio DSP noise reduction, which works after the receiver, cannot do. The two are complementary, not the same.

It covers roughly 500 kHz to 80 MHz - longwave, the AM band, all of HF, and 6 meters - and can stay inline with a transmitter: it passes up to 250 watts and senses transmit RF to bypass itself automatically in a few milliseconds. The main antenna and radio use SO-239 jacks; the noise antenna connects through a phono jack. There is about 6 dB of insertion loss, the price of the cancellation. The design originated at JPS Communications and is now made by Timewave, whose current production version is the ANC-4+ with a dedicated transmit-control input.

It does the same job as the MFJ-1026, and side-by-side tests rate the two about equal for nulling power; the MFJ adds a gain control for the main antenna and a built-in whip, while the Timewave is the more solidly built box. The simpler MFJ-1025 does the same job without the built-in antenna. For an operator fighting one dominant local noise source, any of them can turn an unusable band quiet again.